import math
x1,y1,x2,y2=[float(x) for x in input().split(' ')]
dis=math.sqrt((y2 - y1)**2 + (x2-x1)**2)
print("{:.4f}".format(dis))

 import math math float(x) for x in input().split(' ') for x in input().split(' ') x input().split(' ') ().split () input split ' ' for x in input().split(' ') float(x) float x x1,y1,x2,y2=[float(x) for x in input().split(' ')] x1 [float(x) for x in input().split(' ')] y1 x2 y2 dis=math.sqrt((y2 - y1)**2 + (x2-x1)**2) dis math.sqrt((y2 - y1)**2 + (x2-x1)**2) math.sqrt math sqrt (y2 - y1)**2 + (x2-x1)**2 (y2 - y1)**2 y2 - y1 y2 y1 2 (x2-x1)**2 x2-x1 x2 x1 2 print("{:.4f}".format(dis)) print "{:.4f}".format(dis) "{:.4f}".format "{:.4f}" format dis x1,y1,x2,y2=[float(x) for x in input().split(' ')] [float(x) for x in input().split(' ')] x1 dis=math.sqrt((y2 - y1)**2 + (x2-x1)**2) math.sqrt((y2 - y1)**2 + (x2-x1)**2) dis y2=[float(x) for x in input().split(' ')] [float(x) for x in input().split(' ')] y2 y1,x2,y2=[float(x) for x in input().split(' ')] [float(x) for x in input().split(' ')] y1 x2,y2=[float(x) for x in input().split(' ')] [float(x) for x in input().split(' ')] x2
import math
x1,y1,x2,y2=[float(x) for x in input().split(' ')]
dis=math.sqrt((y2 - y1)**2 + (x2-x1)**2)
print("{:.4f}".format(dis))


